Menstrual cycle

From Ganfyd

Cyclical, approximately monthly vaginal bleeding in women of reproductive age caused by shedding of the endometrium in the absence of implantation of a embryo.

The menstrual period occurs about 14 days after ovulation, unless pregnancy occurs. Ovulation is somewhat variable and unpredictable. Women whose periods are infrequent cannot count on being infertile.

Menstruation

1. Spiral arteries contract for 4-24 hours
2. Spiral arteries dilates
3. blood lakes form, haemorrhage into endometrium
4. fibrin plugs, platelet aggregation
5. spiral arteries constrict
6. epithelium shed
7. re-epithelisation (under oestrogen control)

Disorders of menstruation

Menorrhagia

uterine bleeding, excessive in amount and/or duration of flow occurring at regular intervals

Dysmenorrhoea

painful periods

Oligomenorrhoea

infrequent, irregular episodes of bleeding usually occurring at intervals of more than 40 days

Polymenorrhoea

frequent but regular episodes of uterine bleeding, usually occurring at intervals of less than 21 days

Metrorrhagia

uterine bleeding, usually not excessive but occurring at irregular intervals

Menometrorrhagia

uterine bleeding, usually excessive and prolonged occurring at frequent irregular intervals

Hypomenorrhoea

uterine bleeding, regular but decreased in amount

Intermenstrual bleeding

uterine bleeding, usually not excessive occurring between otherwise regular uterine cycles

See also

• Delaying menstruation